Spend a fair amount of time in traffic,all sorts of situations,one of my most notable.is medium size / length roads (20-40 mph),one of the majors i've noticed particulerly,is following behind diesel vehicles...in the main sedans/suv's - frankly some if the clouds of black smoke coming out the back of those vehicles.i find it hard to come to terms how it could be allowed.!,started to make me think of wearing some form of filtration mask, Do you wear any form of face protection,for whatever reason.?.
Other than a bandana over my face nope. But then once im out of city centre don't need it much and I love my diesel cars used to use one of these though - http://www.ebay.co.uk/itm/BIKE-MOTO...t=LH_DefaultDomain_3&var=&hash=item1e8811487f cheap and cheerful, did the job well.
i use a bandana/buff, mainly because i get fed up of eating bugs..... we dont get the traffic like the uk over here though.